Recently there has been considerable interest in forming composite materials consisting of a polymer matrix having an exfoliated layered material dispersed in the polymer matrix.
One approach to forming such composites involves polymerizing a monomer in the presence of layered material pre-treated with a swelling agent (see U.S. Pat. No. 4,810,734 and U.S. Pat. No. 4,889,885).
In PCT published application WO 93/04118 a process is disclosed for forming a polymeric nanocomposites using a melt-processible polymer and a swellable and polymer compatible intercalated layer material. Although the publication discloses compatibilizing agents suitable for use with polymers such as polyolefms, polyesters and polyamides no procedure is disclosed for predicting the utility of a compatibilizing agent with other classes of polymers.
In U.S. Pat. No. 5,552,469 an intercalate capable of being exfoliated in a polymer matrix is disclosed. The intercalate consists of a layered material swelled by water and a water soluble polymer.
U.S. Pat. No. 5,576,372 and U.S. Pat. No. 5,576,373 disclose a nanocomposite comprising a rubber which has a positively charged group, and a layered silicate that has a negative charge on the silicate whereby the negative charge on the silicate is connected to the positive charge on the reactive rubber through ionic bonding or association thereby overcoming the bonding force between the layers of the silicate resulting in their separation. Nonionic (charge neutral) polymers are not taught.
U.S. Pat. No. 4,889,885 discloses nanocomposites comprising certain resins and a layered silicate dispersed therein, said layered silicate having a layer thickness of 7-12 .ANG. and an interlayer distance of 30 .ANG. or above. Based on the x-ray diffraction data the compositions are entirely exfoliated.
Notwithstanding the foregoing, practical application of nanocomposite materials appears at best to be very limited. Research has therefore been effected to incorporate layered minerals in a polymer matrix in such a way as to provide a material with improved properties. Applicants' invention addresses these needs.